48 ON SPORE DIFFUSION IN THE LARGER ELVELLACEI. 
inch in their short — yet they could distinctly be seen to be bodies 
having length and breadth. 
That the process above described is the normal mode in which 
the sporidia of the Morchellce are diffused, and not the result of 
an accidental chain of circumstances, is further shown in another 
way. A lady, who has a particularly irritable skin, and who has 
often accompanied me in my mycological excursions, was never able 
to gather Morells without suffering from a very unpleasant ery- 
thema of the face, the explanation of which was never arrived at 
until the above observations were made, although experience had 
taught her that the Morells must always be kept at arm’s-length. 
What particularly struck me when observing these spores being 
given off, was the facility with which they floated in the air, having 
little or no tendency to subside. Their specific gravity must be 
very low, and this, aided by their gyrations, will account for the 
extensive and, when aided by air-currents, rapid diffusion of Elvel- 
laceous sporidia. 
DR. MINKS ON THE STRUCTURE OF LICHENS. 
You have favoured me with a copy of No. 49 of “ Grevillea,” 
containing a paper on the letter which I published in the “ Revue 
Mycol.,” No. 7, for the French-speaking public, especially for the 
readers of that journal — a favour for which I thank you most 
sincerely. 
The intention of Mr. Phillips has certainly deserved the acknow- 
ledgments of the English public, but they may decide with what 
success he has solved his theme. 
In order to enable the readers to completely understand my recti- 
fication, the necessity of which appears both urgent and indis- 
pensable, I subjoin the following sketch: — 
The three tissues of the body of lichens, the recently-discovered 
hyphema, the gonohyphema (formerly the hyphoidal system), and 
the gonidema, are not separated from each other by sharp limits ; 
they are only modifications of a single anatomical principle, created 
for physiological and morphological ends. Each tissue contains in 
its cells at least one microgonidium. That not all the cells of 
these tissues, notwithstanding their including green corpuscles, 
appear green in the microscope image, reposes simply on optical 
conditions. The intensity of green colour of the goiiidia does not 
depend, as Mr. Phillips inaccurately translated, on the niicrogo- 
nidia, but on the intensity of their colour, and much more on the 
number and arrangement of these corpuscles in each cell. That 
explains how, not only real hyplue, but also true gonidia, with 
their products, can aj^pear now colourless, now green. Mr. Phil- 
lips, after correctly translating my precise definition — that the 
microgonidium is the criterion of the cell of lichens in opposition 
